Intense chorus waves mitigate the loss of outer radiation belt relativistic electrons during storm main phase

Abstract

We investigate the effects of intense chorus waves (wave power > 10-4 nT2) on relativistic electrons (E > 0.5 MeV) in the heart of the outer radiation belt (L* = 4 - 6) using superposed epoch approach. Combining electron flux and electromagnetic wave measurements from 70 geomagnetic storms during the Van Allen Probes mission, we show the relationship between integrated chorus wave power (0.1 - 0.8 equatorial electron gyrofrequency) and changes in relativistic electron flux on two hour timescales. During the loss-dominated storm main phase (Superposed Epoch -0.5 to 0 days), intense chorus waves mitigate the net loss of relativistic electrons. Conversely, in the early recovery phase (Superposed epoch 0 to 0.5 days), flux increases across a range of relativistic energies regardless of chorus wave power. The amount of electron flux at keV energies appears to have an influence on the consequences of chorus wave activity during geomagnetic storms.